Gel electrophoresis is a standard tool in molecular biology to separate molecular components, such as DNA, RNA or protein, either for subsequent identification or in a preparative procedure. In gel electrophoresis, the different mobility of ions under the influence of an electric field (a function of electrical charge and/or density) serves to separate molecular fragments as they traverse the porous medium. It is common to then transfer the separated fragments to a membrane that binds the fragments permitting further processing directed toward making an image ("blot") visible so that identification can be accomplished.
Ordinarily this transfer is done with the fragments of DNA or the like separated into bands distributed along the body of the gel. The driving force is removed when adequate separation has occurred. A membrane, usually a nylon, is placed on top of the gel so that the bands transfer laterally to the membrane. This is known as a Southern Blot and many variations are available.
An alternate procedure, direct blot, is described by Pohl in U.S. Pat. Nos. 4,631,120 and 4,631,122. There the DNA fragments are run to the end of the gel and transferred to a moving belt that is in contact with the end of the gel. Pohl teaches concentration by angled contact and programmed velocity. Pohl does not teach the use of a prepackaged and disposable gel cassette in conjunction with direct blot.
In U.S. Pat. No. 5,234,559 incorporated by reference herein, there is disclosed an improved direct blot process and apparatus in which the separated fragments are transferred from the end of the gel to a moving membrane that is held on a frame. The framed membrane is then subjected to the further manual or automatic processing steps required to make an image visible for identification such as the steps described in U.S. Pat. Nos. 4,717,653 and 5,087,558 by Webster, Jr. which can be followed by analysis such as that described by Hubner in U.S. Pat. No. 4,885,697.
For convenience of handling and to insure accurate alignment in use, the gel in the apparatus of that application is held in a cassette which is cleaned after each use and reused. It is one object of the instant invention to avoid cleaning and reuse by providing a prepackaged and disposable gel cassette. Prepackaged gels per se are known, but none are in a cassette for direct blot.
It is an object of the instant invention to provide a disposable gel cassette for direct blot procedures. It is a further object to provide such a cassette in a system in which the images obtained have bands which are well separated and with enhanced concentration. To that end the cassette of the instant invention provides an internal angle near the contact to reduce the gel thickness and concentrate the fragments. The apparatus of U.S. Pat. No. 5,234,559 in which the instant gel cassette is useful provides programmed velocity. Still further objects of the invention are to provide a gel cassette which is conveniently filled in the gel casting process, easily packaged for safe shipping, low cost, and convenient to insert into and remove from the apparatus in the field.